Business hours areused to specify the days and hours when your company's employees work. You can create multiple sets of business hours for different time zones or regions and assign them to users based on their location or function. To meet the requirement of having different business hours for reps on pacific time and eastern time, you need to create one set of business hours per time zone and assign them accordingly.
References: https://help.salesforce.com/s/articleView?id=sf.customize_supporthours.htm&type=5https://help.
salesforce.com/s/articleView?id=sf.customize_supporthours_assign.htm&type=5